1. Field of the Invention
The present invention relates to a method for sensing a water level and vibration of a washtub for a washing machine based the amount of a laundry, and in particular, to a method and apparatus for accurately sensing a water level and vibration by detecting an abnormal vibration caused by an inclination of the laundry during a dehydration process of a washing control mode as a LC resonant frequency for thereby optimizing a washing control operation and implementing an accurate detection of a water level and vibration of a washing machine.
2. Description of the Background Art
Generally, a washing machine is designed to detect the amount of a laundry in a washtub. When the amount of the laundry is detected, the water level, the amount of a detergent, and the entire washing time are determined based on the thusly detected amount of the laundry.
Based upon the total washing time required, the washing machine executes a washing operation in which the water within the washtub swirls based on the operation of a pulsator to form a frictional force against the laundry for thereby washing the laundry.
After the washing operation, the washing machine discharges the polluted water to the outside of the washtub and then execute a rinsing operation in which a fresh water is supplied into the washtub to rinse the laundry by the preset number of times.
After the rinsing operation, the washing machine discharges the water to the outside of the washtub and then executes a dehydration operation in which an induction motor rotates at a certain high speed for thereby dehydrating the laundry based on a centrifugal separation force.
In the washing operation control of the washing machine, at an initial washing stage, the washing machine opens a water supply valve to receive a certain amount of water in accordance with the amount of the laundry within the washtub, until the water level reaches a set water level. At this time, as a water level sensing method, there is known a sensing method in which a LC resonant frequency is varied based on the pressure of water supplied within the washtub.
By way of example, if the pressure of water supplied within the washtub is varied, the LC resonant frequency is varied correspondingly thereto. Then, after the varied LC resonant frequency has been measured, the water level corresponding to the amount of the laundry is determined and the water supply valve is closed to stop the supply of water for thereby implementing a proper water level.
During the dehydration operation, since the motor is typically set to rotate at a high speed of about 1700 rotations per minute, a great centrifugal force is generated and drastically affects the laundry within the dehydration tub to thereby cause a strong vibration or noise. Meanwhile, the vibration can not be fully absorbed by means of a balancing device such as a snubber bar which is installed at an upper end portion of the washtub.
In addition, the rotation of the dehydration tub is stopped in accordance with a control of the induction motor. However, since the rotating force caused due to inertia is varied in accordance with the amount of the washing water, the rotation of the dehydration tub is temporarily decreased. In the case that the induction motor is stopped, it is gradually increased. Accordingly, it fails to control the rotation of the dehydration tub to prevent the generation of the vibration and noises.
To overcome the above problems, an improved washing machine capable of sensing the water level and vibration within the washtub during the washing operation is disclosed.
The above improved washing machine has a water level sensor and a vibration sensor. For instance, during the washing and rinsing operations, the water level sensor serves to supply and sense the optimal water level within the washtub, and during the dehydration operation, the vibration sensor functions to sense the vibration generated in the washing machine.
FIGS. 1 to 6 illustrate a conventional washing machine in which a water level sensor and a vibration sensor are installed independently.
As shown therein, the washing machine including a water level sensor and a vibration sensor includes a tank 100 installed within a casing 102 and having an opened top portion and a closed bottom portion, a snubber bar 107 lying between dampers 108 which are respectively assembled at the upper portion of the casing 102 and the lower portion of the tank 100 for absorbing the impact of the tank 100, a washing and dehydration tub (hereinafter, called as a washtub) 101 installed in the interior of the tank 100 and mounted in a coaxial state with the tank 100 to execute the washing and dehydration operations, the washtub forming a plurality of conically shaped holes on the surface thereof, an induction motor 103 installed at a lower portion of the outer surface of the tank 100 for implementing a reverse rotation, a clutch 104 assembled with the induction motor 103 by means of a pulley belt 105 for delivering and decelerating the rotating force of the induction motor 103, a pulsator 106 rotatably installed on the inner bottom surface of the washtub 101 and interposed between the washtub 101 and the clutch 104 for swirling the water within the washtub 101, a water supply valve 109 connected with a water supply path installed at the upper portion of the tank 100 for supplying the water into the washtub 101, a water discharging valve 110 installed on the bottom surface of the tank 100 for discharging the polluted water to the outside of the washtub 101, a vibration sensor 112 installed on the inner surface of one side of the upper portion of the casing 102 for sensing the vibration formed by the contact with the tank 100 due to an eccentric rotation of the washtub 101 in accordance with an eccentrically formed laundry in a certain direction, a water pressure transfer path 113 having one end connected to the lower surface of the tank 100 and the other end vertically extended to the upper portion of the tank 100 for transferring the water pressure generated in accordance with the variation of the water level within the washtub 101, a water level sensor 111 installed at the other end of the water pressure transfer path 113 for changing and outputting an inherent inductance in accordance with the transferred water pressure, a waveform shaping unit 116 for applying a fixed capacitance to the changed value of the inherent inductance to thereby generate a resonant frequency and for then stabilizing the generated resonant frequency with a voltage waveform to thereby amplify and output the resonant frequency, and a microprocessor 114 for determining the vibration and the water level with the vibration sensed by the vibration sensor 112 and the voltage waveform inputted through the waveform shaping unit 116 and for controlling the operation of the induction motor 103 using a motor driving member 115 and the opening and closing operation of the water supply and discharging valves 109 and 110 and a valve driving member 117 in accordance with the determined vibration and the water level. FIGS. 2 and 3 illustrate the detailed configuration of the water level sensor 111 as shown in FIG. 1.
The water level sensor 111 is comprised of a cylindrical housing 10 which has a through hole connected through the water pressure transfer path 113 to the tank 100 at one side thereof and an opening hole at the other side thereof, a bellows 11 which is installed within the housing 10 and is connected to the water pressure transfer path 113 to be extended or expanded in accordance with the pressure of water within the washtub 101, a shielding member 12 which is sealed at the top portion of the bellows 11 and have a hook shape to shield the water pressure, a cylindrical coil 14 having an inherent inductance value, which is installed at the center portion of the inner wall of the housing 10 to be separated by a predetermined distance in a vertical direction from the shielding member 12, a cylindrical core 13 which is hooked at the upper portion of the shielding member 12 and moves vertically in the internal space of the coil 14 in accordance with the extension and expansion of the bellows 11 to thereby vary the inherent inductance value of the coil 14, a cylindrical support member 16 which is assembled at the top end portion of the coil 14 and serves to support the coil 14 against the housing 10, a cap 17 which is adapted to cover the opening at the top end portion of the support member 16, and a coil shape spring 15 which is interposed between the top surface of the core 13 and the bottom surface of the cap 17 to restore the core 13 to the original position thereof.
The waveform shaping unit 116, as shown in FIG. 6, is comprised of an amplifier 116a which amplifies an input voltage to a substantial voltage size to provide the amplified voltage to the microprocessor 114, and condensers C1 and C2 which are respectively connected in serial with the input and output terminals of the amplifier 116a via resistors R1 and R2 and feed back the output voltage from the amplifier 116a to the input voltage thereof. In this case, the waveform shaping unit 116 is operated based on a LC resonant circuit configuration in such a manner that both terminals a and b of the coil 14 are respectively connected in parallel with the condensers C1 and C2, and the core 13 moves vertically in the internal space of the coil 14.
The vibration sensor 112 such as a safety switch or a limit switch, as shown in FIG. 5, is comprised of first and second voltage discontinuous members 22 and 23 which are respectively installed at the upper portion of the casing 102 and is electrically short-circuited or opened, a switch leg 20 which is hinged to the first voltage discontinuous member 22 to be separated at a predetermined distance from the tank 100 and rotates by the striking of the tank 100 according to the rotation radius of the washtub 101 to electrically short-circuit the first and second voltage discontinuous members 22 and 23, and a spring 21 which restores the switch leg 20 to the original position thereof to electrically open the first and second voltage discontinuous members 22 and 23. An explanation of the operation of the conventional washing machine in which the water level sensor and the vibration sensor are installed, respectively will be discussed in detail with reference to FIGS. 1 to 6.
Firstly, if an operation is started after the washing operation has been set through an operational panel (not shown), the microprocessor 114 controls the water supply valve 109, the water discharging valve 110 and the induction motor 103 through the valve driving member 117 and the motor driving member 115 to thereby execute the washing, rinsing and dehydration operations in a scheduled sequence.
At this time, the microprocessor 114 receives an input signal, which is generated in accordance with the operation states of the water level sensor 111 sensing the water level of the washtub 101 and the vibration sensor 112 sensing the vibration of the washtub 101, and then outputs a control signal in response to the input signal.
In this case, the microprocessor 114 meets the following conditions. It recognizes the state where the core 13 of the water level sensor 111, as will be described in detail, is not advanced into the internal space of the coil 14, as the state where the water is not retained within the washtub 101, i.e. the water level of zero, and contrarily, recognizes the state where the core 13 of the water level sensor 111 moves vertically the internal space of the coil 14, as the state where the water is retained within the washtub 101 based upon the movement of the core 13.
Under the above conditions, the microprocessor 114 controls, for the purpose of supplying the water within the washtub 101 upon an initial washing operation, the valve driving member 117 to open the water feeding valve 109 such as an electronic control valve in accordance with the amount of the laundry retained within the washtub 101.
If the water is fed into the washtub 101, the water pressure becomes high. Then, the water pressure is applied, through the water pressure transfer path 113 connected to the tank 100, to the bellows 11 within the housing 10 of the water level sensor 111. At this time, the shielding member 12, which is sealed at the upper portion of the bellows 11, prevents the water pressure from being continuously increased. This results in the generation of pressure expansion. Thereby, the pressure expansion renders the bellows 11 expanded in proportion to the water pressure.
Referring to FIG. 4, if the bellows 11 is expanded, the cylindrical core 13, which is assembled with the shielding member 12, moves in the internal space of the coil 14 upwardly in the vertical direction, in step ST10. The coil 14 has a diameter larger than that of the core 13 and includes the inherent inductance value. The inherent inductance value is varied in accordance with the upward movement of the core 13, in step ST20. For example, the inherent inductance value is increased as the core 13 moves in the internal space of the coil 14 in the upward direction.
The inductance variation value of the coil 14 is multiplied by a capacitance value of the condensers C1 and C2 of the waveform shaping unit 116 of FIG. 6 to be produced as a predetermined resonant frequency. The resonant frequency is shaped into a voltage waveform by the waveform shaping unit 116 and is then supplied to the microprocessor 114.
In other words, the both terminals a and b of the coil 14 of the water level sensor 111 are respectively connected in parallel with the condensers C1 and C2 of the waveform shaping unit 116. As a result, the waveform shaping unit 116 is operated based on a single LC resonant circuit configuration by the arrangement of the coil 14 and the condensers C1 and C2, thus to generate the resonant frequency, at step ST30.
Conventionally, the resonant frequency f.sub.0 of the LC resonant circuit is calculated under the following equation: ##EQU1##
The resonant frequency f.sub.0 is amplified by the amplifier 116a to a substantial voltage size, and the amplified voltage waveform is provided to the microprocessor 114.
The microprocessor 114 measures the water level within the washtub 101 on the basis of the resonant frequency f.sub.0 of the waveform shaping unit 116 generated based on the inductance variation value of the water level sensor 111. Then, it determines as to whether the measured water level is optimal to correspond with the amount of the laundry detected. If determined as optimal, it controls the valve driving member 117 to close the water supply valve 107.
Thereafter, it controls the motor driving member 115 to alternatively electrify the induction motor 103, which renders the pulsator 106 to be forwardly and reversely rotated in turn.
As a result, the water within the washtub 101 is swirled, which causes the frictional force against the laundry to be generated, thus to execute the washing operation.
If the washing operation is completed, the microprocessor 114 controls the valve driving member 117 to open the water discharging valve 110 and discharges the polluted water to the outside of the washtub 101. At the time, the water level sensor 111 senses whether the polluted water within the washtub 101 is completely discharged.
In other words, during the discharging operation, the water pressure is decreased as the water level within the washtub 101 is low. Accordingly, if the water pressure is increasingly decreased, the bellows 11 is expanded, based upon the elastic force of the spring 15, which is interposed between the cap 17 and the core 13 of the water level sensor 111. Moreover, the core 13 gradually descends vertically in the internal space of the coil 14, thereby returning to the initial position thereof.
If the core 13 is returned to the initial position thereof, the inductance value of the coil 14 is also decreased. Hence, the resonant frequency f.sub.0, which is obtained by multiplying the inductance variation value of the coil 14 by the capacitance value of the condensers C1 and C2, is changed to the initial value thereof and then inputted to the microprocessor 114. As a result, the microprocessor 114 determines the completion time of the discharging operation.
After the completion of the washing operation, the rinsing operation is implemented through the water feeding and discharging to/from the washtub 101, as mentioned above.
For the dehydration operation after the washing and rinsing operations are performed, the microprocessor 114 controls the induction motor 103 to be rotated at a set rotation speed and senses the vibration generated within the washtub 101 due to the rotation of the induction motor 103 by means of the vibration sensor 112 as shown in FIG. 5.
During the dehydration operation, an appropriate balance or an undesirable vibration within the tank 100 is generated in accordance with the collection of the laundry in a certain direction.
If the laundry is uniformly disposed at the internal wall of the washtub 101, the vibration within the washtub 101 caused due to the rotation speed of the induction motor 103 is not generated after a little amount of vibration has been generated. As a result, the washtub 101 finally reaches a normal dehydration speed, while having the same rotation radius centering around the concentric axis. This creates a balancing state where no vibration within the tank 100 is generated, thus to execute the normal dehydration operation during the set time period.
On the other hand, if the laundry is inclined at a certain corner of the wall of the washtub 101, the washtub 101 eccentrically rotates in every direction as the rotation speed is high, and if the eccentric rotation is severe, the tank 100 undesirably strikes against the washtub 101.
The vibration width is increased in accordance with the strength of the striking at the tank 100, and as shown in FIG. 5, the switch leg 20 of the vibration sensor 112 such as the safety switch or the limit switch is struck at every rotation. Thereby, the switch leg 20 electrically short-circuits or opens the first and second voltage discontinuous members 22 and 23, while rotating counterclockwise or clockwise by means of the spring 21.
If the microprocessor 114 inputs an electrical signal from any one of the first and second voltage discontinuous members 22 and 23, it controls the water supply valve 109 to supply the water within the washtub 101 and thus executes an untwisting operation for the laundry during a predetermined time period. Thereby, the laundry can be uniformly disposed on the wall surface of the washtub 101 to thereby reduce the strength of the vibration formed.
If the vibration is decreased, the microprocessor 114 controls the motor driving member 115 to rotate the induction motor 103 at a high speed, thereby completing the dehydration operation.
Meanwhile, if the microprocessor 114 continuously inputs the electrical signal from the corresponding voltage discontinuous member, after the untwisting operation for the wash, it halts the induction motor 103 to thereby prevent the generation of the over-vibration.
It can be appreciated that the water level and vibration sensing device in the conventional washing machine is capable of sensing, during the washing operation for the wash, the water level of the washtub using the LC resonant circuit in which an inductance variation value of the coil within the water level sensor is calculated and sensing, during the dehydration operation for the wash, the vibration within the washtub using the separate vibration senor such as a limit switch.
As known, however, since the conventional washing machine should include independent water level sensor and vibration sensor, there are some problems in that the production cost is high and a manufacturing process is complicate.
In addition, since the vibration sensor uses mechanical contact points and a spring, there is a problem in that malfunctions may be generated due to the aged deterioration or corrosion of the contact points. Furthermore, it is impossible for the conventional vibration sensor to accurately sense the vibration within the washtub because of the necessity of the adjustment of the intervals of the contact points and the decrement of the restoring force of the spring.
By way of example, if the vibration sensor is installed adjacent to the tank, it senses a slight vibration of the tank, which causes the washing machine to execute an unnecessary operation. However, if installed at some distance, it does not sense the vibration until the vibration becomes severe. Therefore, so as to dispose the initial position of the vibration sensor in an accurate manner, an additional production cost should be required and a productivity efficiency may be degraded.
Accordingly, there is a need to provide an improved water level and vibration sensing device which can solve the above problems experienced in the conventional washing machine and cam be manufactured with relative low production cost and high reliability.